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Thin Film Thickness / Spectrometer

Film Thickness Measurements are one of the most challenging and critical metrics in any coating process. Destructive testing can be used to measure the thickness of a film from a cross-section, however (besides the undesirability of a broken product), the method of breakage may impact the measurement (a cutting tool may compress it, a cleave plane may result in delamination). Non-destructive optical testing is preferred, but, buying separate tools for profiling and film thickness measurements is not cost effective for most labs and small companies. Combining a film spectrometer with an optical profiler is an ideal solution.

Zeta Film Thickness (ZFT)

Zeta Film Thickness option is available on all Zeta3D™ models:

Additional tool capability without the cost or the floor space overhead

Works well on samples with large film thickness non-uniformity

Can measure films thicker than 30 nm and up to 100 microns in thickness

Industry challenges addressed by ZFT

Many separate tools to complete measurements

Destructive testing

Inaccurate location data

Convenience

Slow Speed

No Cost Savings

Technology

The ZFT (Zeta Film Thickness) option on the Zeta3D™ Optical Profilers is a white light based broadband spectroscopic reflectometer that is capable of measuring multi-stack film thickness or n&K values if the thickness is known. It uses a common light source, optics path and camera, so that the film thickness measurements are in the same location as the 3D surface profile measurements.

Transparent or semi-transparent films

ITO (Indium Tin Oxide) Thickness

Display manufacturers use the Zeta3D Optical Profilers extensively, and by adding the functionality of reflectometry, enjoy time- and cost-savings in their process. Transparent conductive oxides (TCOs), such as indium tin oxide (ITO), are used in display manufacturing to transport current to each light-emitting element. While many thin films are used in the process, ITO has a unique spectral signal that generally dominates all others, making measurements extremely challenging. By using the refractive index of the ITO layer in the ZFT memory, the thickness of its’ layer, as well as other film layers, are measured.

Plated Copper thickness with photoresist intact

Controlling plated copper uniformity on a production wafer has always been a challenge for the semiconductor industry. Copper is non-transparent, making the plating thickness impossible to measure using traditional optical means. Improper plating thickness impacts device performance, or, in the worst case, loss of a valuable wafer. The Zeta3D Optical Profiler with the ZFT option provides a huge advantage. Not only can the ZFT measure the thickness of the photoresist (shown right), the profiler option can measure the depth of the plated copper. The copper plating thickness can be determined without stripping the photoresist. The wafer can be reworked at minimal cost, thus improving fab yield.

73.5nm Nitride Film on Rough c-Si Solar Cell

ZFT has no problem measuring the thickness of films on textured c-Si surfaces. Solar-grade silicon (c-Si) surfaces are roughened in order to decrease reflection losses at the front surface of silicon wafer solar cells. The ZFT works on some of the least reflective surfaces such as a solar cell with reflectivity of less than 0.5%. Many film thickness tool have difficulty in obtaining any signal from these type of surfaces. The proprietary Zeta3D illuminator design with broadband white light sources allow the tool to be used with a variety of optically transparent films on textured c-Si surfaces.

3.0μm (nominal) PMMA Film on Cu

Spin-coating photoresist onto flat wafers is a standard process, but spin-coating on a patterned surface may yield localized film non-uniformity. Shown here is a patterned device, spin-coated with PMMA. The 3D image is shown, and due to the Zeta3D’s live view capability, measurements of the PMMA thickness at different points can be taken across the device.

Contact Us Today

Proper characterization of film thickness is critical for developing processes in advanced industries such as semiconductors, solar, and display. Allow Zeta Instruments to help you advance your research and manufacturing technology today.

Call us at (855) 405-8008

Testimonials

“In our older fabs, we use five different metrology tools to monitor various process steps on both 8” and 12” wafers. In our new fab, we only use the Zeta-580. The Zeta multi-mode optical profiler is so powerful and easy to use, our operators love it. I am so happy with the decision we made to purchase the Zeta-580 for our new fab.”

– Fab Manager –

Advanced Packaging FabTaiwan

“Unlike other optical profilers, the Zeta can accurately measure reflowed bump heights in the presence of passivation layers. We now rely on the Zeta to calibrate all of our expensive bump inspection systems.”